Topological Defects and Interactions in Nematic Emulsions

TL;DR

This paper provides a theoretical analysis of topological defects and dipolar interactions in nematic emulsions, explaining how droplets induce defects and chain formation in the nematic host.

Contribution

It introduces a variational approach to model defect formation and droplet interactions, revealing the energetically favored dipole configuration in nematic emulsions.

Findings

A single droplet acts like a hedgehog defect in the nematic host.

Droplet-induced distortions lead to dipole-dipole interactions and chaining.

The lowest energy state involves a tightly bound droplet-hedgehog dipole.

Abstract

Inverse nematic emulsions in which surfactant-coated water droplets are dispersed in a nematic host fluid have distinctive properties that set them apart from dispersions of two isotropic fluids or of nematic droplets in an isotropic fluid. We present a comprehensive theoretical study of the distortions produced in the nematic host by the dispersed droplets and of solvent mediated dipolar interactions between droplets that lead to their experimentally observed chaining. A single droplet in a nematic host acts like a macroscopic hedgehog defect. Global boundary conditions force the nucleation of compensating topological defects in the nematic host. Using variational techniques, we show that in the lowest energy configuration, a single water droplet draws a single hedgehog out of the nematic host to form a tightly bound dipole. Configurations in which the water droplet is encircled by a disclination ring have higher energy. The droplet-dipole induces distortions in the nematic host that lead to an effective dipole-dipole interaction between droplets and hence to chaining.